FBI releases photos from Navy Yard shooting

This image taken from security cameras and released by the FBI on September 25, 2013, shows Washington Navy Yard shooter Aaron Alexis moving through the hallways of Building #197 carrying the Remington 870 shotgun. Twelve people were killed in the September 16, 2013, shooting. AFP PHOTO / FBI

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Aaron Alexis moves through the hallways of Building #197 carrying a Remington 870 shotgun in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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Aaron Alexis moves through the hallways of Building #197 carrying a Remington 870 shotgun in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout

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Aaron Alexis drives his rental car, a blue Toyota Prius, through the Washington Navy Yard main gate in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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This image taken from security cameras and released by the FBI on September 25, 2013, shows Washington Navy Yard shooter Aaron Alexis driving into a parking garage before entering Building #197. Alexis had legitimate access to the Washington Navy Yard as a result of his work as a contractor, and he utilized a valid pass to gain entry to the building, the FBI said. Twelve people were killed in the September 16, 2013, shooting. AFP PHOTO / FBI

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This image from video released by the FBI(Federal Bureau of Investigation) on September 25, 2013, shows a Toyota Prius that was driven by Aaron Alexis to the Navy Yard in Washington, DC on September 16, before going on a shooting spree. Thirteen people, including the gunman Aaron Alexis, were killed in the incident. AFP PHOTO / HANDOUT / FBI

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Aaron Alexis enters Building #197 at 8:08 a.m., carrying a backpack, in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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This image released by the FBI(Federal Bureau of Investigation) on September 25, 2013, shows a backpack hanging in stall in a fourth-floor bathroom that was carried by Aaron Alexis into Navy Yard building 197 in Washington, DC on September 16, before going on a shooting spree. Thirteen people, including the gunman Aaron Alexis, were killed in the incident. AFP PHOTO / HANDOUT / FBI

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Aaron Alexis' Remington 870 shotgun with sawed-off barrel and stock is pictured in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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Aaron Alexis' Remington 870 shotgun with sawed-off barrel and stock is pictured in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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Aaron Alexis' Remington 870 shotgun with sawed-off barrel and stock is pictured in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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Aaron Alexis' Remington 870 shotgun with sawed-off barrel and stock is pictured in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters

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Aaron Alexis' Remington 870 shotgun with sawed-off barrel and stock is pictured in this undated handout photo released by the FBI. Over the course of an hour-long shooting incident at the Washington Navy Yard in Washington, DC on September 16, 2013, Aaron Alexis killed 12 people and wounded four others before he was shot and killed by law enforcement officers. REUTERS/FBI/Handout via Reuters